Catalysts containing iron, antimony, and at least one element selected from the group consisting of vanadium, molybdenum, and tungsten are known to be useful in production of aldehydes by oxidation of organic compounds, production of dienes or alkenylbenzenes by oxidative dehydrogenation of organic compounds, and production of nitriles by ammoxidation of organic compounds. Reference can be made, e.g., in U.S. Pat. Nos. 3,445,521, 3,542,843, 3,546,138, and 3,591,620, JP-B-46-2806 (the term "JP-B" as used herein means an "examined published Japanese patent application"), JP-B-46-2807, U.S. Pat. Nos. 3,668,147, 3,988,359, and 4,083,804, JP-B-54-39839, and JP-A-63-250357 (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
On the other hand, production of antimony-containing oxide catalysts inclusive of those useful in the above-mentioned reactions is associated with problems such as poor reproducibility, poor operability, and difficulty of obtaining high strength catalysts. In view of these problems, there have been proposed several improved processes for producing such catalysts as disclosed, e.g., in U.S. Pat. Nos. 3,341,471, 3,686,138 and 4,049,575, JP-B-46-3456, JP-A-63-190646, and JP-A-3-26342 (corresponding to U.S. Ser. No. 07/540,729 filed on Jun. 20, 1990 and EP 404529Al.
However, conventionally proposed processes for producing an antimony-containing oxide catalyst hardly attain good results when applied as such to production of iron. antimony catalysts having high contents of vanadium, molybdenum and tungsten. For example, the processes disclosed in U.S. Pat. Nos. 3,657,155 and 3,686,138 and JP-A-3-26342 are excellent for producing iron.antimony-based metal oxide catalysts suitable for fluidized bed reactions. However, when the processes are applied to production of catalysts containing relatively large quantities of vanadium, molybdenum, and tungsten as purposed in the present invention, the resulting catalysts hardly meet the demands for activity and physical properties as demonstrated in Test Examples hereinafter described. Further, the process disclosed in JP-A-63-190646 in which catalysts are produced by impregnation requires complicated steps for obtaining catalysts containing large quantities of vanadium, molybdenum, and tungsten, for example, repetition of impregnation and drying using an impregnating solution having a low concentration and is not therefore considered to be fully suitable for practical use.
Since the industrial output of products obtained by the oxidation or ammoxidation of organic compounds is high, a slight increase in yield of the desired products or a slight improvement in the physical properties of the catalyst or catalyst strength gives great commercial and economic effects.